1. Field of the Invention
This invention relates to bonded semiconductor structures formed using bonding.
2. Description of the Related Art
Advances in semiconductor manufacturing technology have provided computer systems with integrated circuits that include many millions of active and passive electronic devices, along with the interconnects to provide the desired circuit connections. A typical computer system includes a computer chip, with processor and control circuits, and an external memory chip. As is well-known, most integrated circuits include laterally oriented active and passive electronic devices that are carried on a single major surface of a substrate. The current flow through laterally oriented devices is generally parallel to the single major surface of the substrate. Active devices typically include transistors and passive devices typically include resistors, capacitors, and inductors. However, these laterally oriented devices consume significant amounts of chip area. Sometimes laterally oriented devices are referred to as planar or horizontal devices. Examples of laterally oriented devices can be found in U.S. Pat. No. 6,600,173 to Tiwari, U.S. Pat No. 6,222,251 to Holloway and U.S. Pat. No. 6,331,468 to Aronowitz.
Vertically oriented devices extend in a direction that is generally perpendicular to the single major surface of the substrate. The current flow through vertically oriented devices is generally perpendicular to the single major surface of the substrate. Hence, the current flow through a vertically oriented semiconductor device is generally perpendicular to the current flow through a horizontally oriented semiconductor device. Examples of vertically oriented semiconductor device can be found in U.S. Pat. No. 5,106,775 to Kaga, U.S. Pat. No. 6,229,161 to Nemati and U.S. Pat No. 7,078,739 to Nemati.
It should be noted that U.S. Pat. No. 5,554,870 to Fitch, U.S. Pat. No. 6,229,161 to Nemati and U.S, Pat No. 7,078,739 to Nemati disclose the formation of both horizontal and vertical semiconductor devices on a single major surface of a substrate. However, forming both horizontal and vertical semiconductor devices on a single major surface of a substrate complicates the processing steps because the masks and processing steps needed are not compatible.
Some references disclose forming an electronic device, such as a dynamic random access memory (DRAM) capacitor, by crystallizing polycrystalline and/or amorphous semiconductor material using a laser. One such electronic device is described in U.S. patent Application No. 20040156233 to Bhattacharyya. The laser is used to heat the polycrystalline or amorphous semiconductor material to form a single crystalline semiconductor material. However, a disadvantage of this method is that the laser is capable of driving the temperature of the semiconductor material to be greater than 800 degrees Celsius (° C.). In some situations, the temperature of the semiconductor material is driven to be greater than about 1000° C. It should be noted that some of this heat undesirably flows to other regions of the semiconductor structure proximate to the DRAM capacitor, which can cause damage.
Another type of semiconductor memory is referred to as a static random access memory (SRAM) circuit. There are many different circuits that operate as SRAM memory circuits, with examples being disclosed in U.S. Pat. Nos. 5,047,979, 5,265,047 and 6,259,623. Some SRAM memory circuits include four transistors per unit cell, and others include six transistors per unit cell. In general, an SRAM memory circuit occupies more area as the number of transistors it includes increases. Hence, an SRAM memory circuit having six transistors generally occupies more area than an SRAM memory circuit having four transistors.
The transistors of many SRAM memory circuits are metal oxide field effect (MOSFET) transistors, which can be n-channel or p-channel. An n-channel MOSFET is typically referred to as an NMOS transistor and a p-channel MOSFET is typically referred to as a PMOS transistor. SRAM memory circuits are complementary metal oxide semiconductor (CMOS) circuits when they include NMOS and PMOS transistors connected together. A substrate which carries a CMOS circuit requires a p-type well and an n-type well, wherein the p-type well is used to from the NMOS transistors and the n-type well is used to form the PMOS transistors. The p-type well and n-type well are spaced apart from each other, which undesirably increases the area occupied by the CMOS circuit. Accordingly, it is highly desirable to provide an SRAM circuit which occupies less area.